/*
  Copyright 2019-2020 David Robillard <d@drobilla.net>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

/**
   @file rects.h
   @brief Utilities for rectangle animation demos.

   This file contains common definitions for demos that show an animation of
   many 2D rectangles.
*/

#include <math.h>
#include <stddef.h>

typedef float vec2[2];

typedef struct {
	float pos[2];
	float size[2];
	float fillColor[4];
} Rect;

static const vec2 rectVertices[] = {
    {0.0f, 0.0f}, // TL
    {1.0f, 0.0f}, // TR
    {0.0f, 1.0f}, // BL
    {1.0f, 1.0f}  // BR
};

static const unsigned rectIndices[4] = {0, 1, 2, 3};

/// Make a new rectangle with the given index (each is slightly different)
static inline Rect
makeRect(const size_t index, const float frameWidth)
{
	static const float alpha   = 0.3f;
	const float        minSize = frameWidth / 64.0f;
	const float        maxSize = frameWidth / 6.0f;
	const float        s       = (sinf((float)index) / 2.0f + 0.5f);
	const float        c       = (cosf((float)index) / 2.0f + 0.5f);

	const Rect rect = {
	    {0.0f, 0.0f}, // Position is set later during expose
	    {minSize + s * maxSize, minSize + c * maxSize},
	    {0.0f, s / 2.0f + 0.25f, c / 2.0f + 0.25f, alpha},
	};

	return rect;
}

/// Move `rect` with the given index around in an arbitrary way that looks cool
static inline void
moveRect(Rect* const  rect,
         const size_t index,
         const size_t numRects,
         const float  frameWidth,
         const float  frameHeight,
         const double time)
{
	const float normal    = (float)index / (float)numRects;
	const float offset[2] = {normal * 128.0f, normal * 128.0f};

	rect->pos[0] = (frameWidth - rect->size[0] + offset[0]) *
	               (sinf((float)time * rect->size[0] / 64.0f + normal) + 1.0f) /
	               2.0f;
	rect->pos[1] = (frameHeight - rect->size[1] + offset[1]) *
	               (cosf((float)time * rect->size[1] / 64.0f + normal) + 1.0f) /
	               2.0f;
}